Modeling of Tidal Circulation and Pollutant Transport in Port Angeles Harbor and Strait of Juan de Fuca

Strait of Juan de Fuca is a high tidal energy pathway, which connects the Northeast Pacific Ocean continental shelf to the Strait of Georgia and Puget Sound. Complex circulation patterns, such as strong tidal fronts and eddies are observed in this high tidal energy regime, especially near the complex coastlines. These tidal fronts and eddies have significant effect on the dilution, trapping and transport of effluent discharges. A three-dimensional hydrodynamic model was developed to simulate the tidal circulation and pollutant transport in the eastern region of Strait of Juan de Fuca using the Environmental Fluid Dynamic Code (EFDC). In the present study, the model was driven by major semi-diurnal and diurnal tidal constituents, as well as surface winds. The model domain consists of multiple open boundaries, which connect to the ocean water and a number of estuarine systems. Historical water surface elevation, ADCP data, and surface drogue trajectories were used to calibrate the model over a period covering the spring and neap tidal cycle. To study the tidal eddy and transport processes near the Port Angeles Harbor located on the southeast shores of Strait of Juan de Fuca, a localized high-resolution boundary-fitted model grid was generated. The model successfully reproduced the tidal dynamics in the study area and good agreements between model results and observed data were obtained. The calibrated model was applied to simulate the transport and deposition of total suspended solids (TSS) discharged within the Port Angeles Harbor using weighted average of multiple particle sizes corresponding to typical secondary pulp mill effluent. The TSS deposition rates corresponding to different outfall characteristics were calculated and sediment impact zones in the Port Angeles Harbor area were analyzed.